invalidate

(verb) declare invalid. Synonyms: annul, quash, void, avoid, nullify. Examples: "The contract was annulled." "Void a plea."

(verb) make invalid for use. Synonyms: cancel. Example: "Cancel cheques or tickets."

(verb) show to be invalid. Synonyms: nullify.

(verb) take away the legal force of or render ineffective. Synonyms: void, vitiate. Example: "Invalidate a contract."